Torsional vibration damper

ABSTRACT

A torsional vibration damper comprises a housing adapted to be attached to the crankshaft of an internal combustion engine and an annular weight rotatably mounted in a silicone-filled chamber of the housing. The housing comprises a flat, annular plate secured to an annular case by two electro-beam welds. An O-ring seal is positioned between the plate and case to cooperate with the welds for sealing purpose. Fill ports, adapted to charge the housing&#39;&#39;s chamber with silicone, each have a lead seal and an overlying expansion plug secured therein.

11mm States Patent [191 Baht et al.

[ NOV. 13, 1973 TORSIONAL VIBRATION DAMPER [75 Inventors: Russel F.Bahr; William O.

Jankovsky, both of Peoria; William G. Johnson, Pekin; Duane V. Kolb,Roanoke, all of I11.

[731 Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: July 12, 1971 [21] Appl. No.: 161,638

[52] US. Cl. 74/574, 188/1 B [51] Int. Cl F161 15/12 [58] Field ofSearch 74/574; 188/1 B [56] References Cited UNITED STATES PATENTS3,495,459 2/1970 McLean 74/574 3,512,612 5/1970 Bragg et a1. 188/1 B3,555,926 1/1971 Moorhouse et a1. 188/1 B 2,514,139 7/1950 OConnor74/574 FOREIGN PATENTS OR APPLICATIONS 1,032,572 7/1953 France 74/5741,939,491 2/1970 Germany 74/574 Primary ExaminerCharles J. MyhreAssistant Examiner-F. D. Shoemaker Att0rneyCharles M. Fryer et a1.

[57] ABSTRACT A torsional vibration damper comprises a housing adaptedto be attached to the crankshaft of an internal combustion engine and anannular weight rotatably mounted in a silicone-filled chamber of thehousing. The housing comprises a flat, annular plate secured to anannular case by two electro-beam welds. An O-ring seal is positionedbetween the plate and case to cooperate with the welds for sealingpurpose. Fill ports, adapted to charge the housings chamber withsilicone, each have a lead seal and an overlying expansion plug securedtherein.

1 Claim, 3 Drawing Figures PAIENIEIIHBY I 3 ms 3771; 380

INVENTORS RUSSEL F. BAH R WILLIAM O, JANKOVSKY WILLIAM G. JOHNSON DUANEV. KOLB AT TORNEYS TORSIONAL VIBRATION DAMPER BACKGROUND OF THEINVENTION A torsional vibration damper may be attached to the crankshaftof an internal combustion engine to dampen vibrations occasioned duringoperation thereof. Such vibrations generate dynamic forces which wouldnormally tend to twist the crankshaft and to subject attendantmechanisms to damage. Conventional dampers, such as the ones disclosedin U.S. Pat. Nos. 3,234,817 and 3,512,612, both assigned to the assigneeof this application, have proven highly successful for damping andtuning purposes.

SUMMARY AND OBJECTS OF THIS INVENTION An object of this invention is toprovide a noncomplex and economical housing for a torsional vibrationdamper of the above type which exhibits high degrees of manufacturingcapabilities, structural integrity and performance desiderata.

The damper of this invention comprises an integrated hub and damperhousing having an annular weight rotatably mounted in a chamber thereof.The housing comprises an annular case having three connected wallsdefining such chamber and a flat, annular plate secured to the case byelectro-beam welds. In the preferred embodiment, each weld is recessedby an annular V-shaped groove and an annular seal is positioned betweenthe plate and case for sealing purposes. Fill ports for charging thehousings chamber with a silicone fluid may each be closed by a lead sealand an overlying expansion plug.

DESCRIPTION OF THE DRAWINGS Other objects of this invention will becomeapparent from the following description and accompanying drawingswherein:

FIG. 1 is a cross-sectional view of a torsional vibration damperembodying the present invention, taken in the direction of arrows I1 inFIG. 2;

FIG. 2 is a partially sectioned, side elevational view of a portion ofthe damper; and FIG. 3 is an enlarged, sectional view of the lowerportion of the damper as illustrated in FIG. 1

DESCRIPTION OF THE PREFERRED EMBODIMENT The FIGS. 1-3 damper is disposedon a central rotational axis X and comprises an integrated hub andhousing assembly adapted to be attached to a crankshaft 11 of aninternal combustion engine by circumferentially spaced bolts 12. Thetwo-part housing assembly comprises an annular case 13 and a flatcircular plate 14 secured together by annular electron-beam weld means14 and 16. The case and plate may each comprise a cold rolled SAE 1008,aluminum killed steel, for example, which is particularly adapted forelectron-beam welding.

An annular O-ring seal or sealing means 17 is positioned in a matinggroove 18 formed on case 13', adjacent to and radially inwardly of weld16 (FIG. 3). A closed, annular chamber 19 contains a highly viscous(e.g., one million centistokes) silicone fluid. The chamber is filledvia one of two diametrically disposed port means 20 and the port meansare thereafter closed by means of a lead seal 21 and overlyingWelsh-type expansion plug 22 mounted in a counterbore portion 23.

The second port means is utilized for air purging purposes during thefilling operation.

An annular inertia weight 24 is rotatably mounted in a closed chamber,defined by connected parallel inner and outer walls and a transversesidewall of the case and by plate 14. The weight cooperates with thesurrounding silicone fluid to provide the damping and tuning desiderata.The weight is rotatably mounted on an axially disposed hub or inner wall25 attached to a radially disposed and offset annular flange 26 attachedto crankshaft 11.

The weight may comprise an iron casting or other weighty materialsubstantially covered with a plastic bearing material or coating 27,such as nylon, Teflon or bronze having a uniform thickness approximating0.015 in., secured on a conventional primer 28, such as a 253-P primermanufactured by the M&T Chemical Co. In addition to the bearing contactprovided, the plastic material prevents contact between the metallicweight and housing.

A plurality of radial passages 29 are formed through the weight andcoating 27 to communicate the highly v viscous silicone fluid fromchamber portions 30 to clearances 31, defined between the weight and thesidewalls and outer wall of the housing. The clearances are preciselydefined and maintained during damper operation by means of axiallyaligned annular shoulders or spacing means 32 and 33, formed at theradially inner portion of the weight. Chamber portions 30, similar tothose described in US. Pat. No. 3,512,612, normally retain asubstantially large portion of the silicone fluid and are prefabricatedin the form of recesses defined by circumferentially spaced and raisedsurface portions 34 formed on hub 25. One of the passages is preferablytapped at the radially outer end thereof, as shown at 35 in FIG. 1, toprovide threads adapted to have an eye bolt secured therein fortransport purposes during fabrication of the weight.

The damper may be fabricated as taught in US. Patent application Ser.No. 146,257, filed on May 24, 1971 by Gary 0. Bragg et al. The damper isassembled by centering the weight on raised portions 34 of the housingand by seating O-ring seal 17 in groove 18 (FIGS. 1 and 3). Plate 14 isthen secured to case 13 by annular electron-beam welds 15 and 16.

The outer surface of the plate preferably has annular grooves 55 and 56of generally V-shaped cross-section and limited depth pre-formed thereonto assure the desired penetration of welds 15 and 16 through the plateand into the abutting free edge of the outer wall and flange 26 of thecase. In addition, the welds preferably terminate adjacent to the apexof a respective groove so as not to protrude beyond the outer surface ofthe plate which might inhibit correct assembly by a drive pulley or thelike thereon. Also, the welding operator is provided with an accurateline or template by which to weld.

Chamber 19, including chamber portions 30, is thereafter filled with aviscous fluid via one of the ports 20. The second port permits air toescape during the filling operation wherein the damper is maintainedhorizontally. When the chamber has received the proper amount of fluid,lead seals 21 are placed within counterbores 23 of ports 20 (FIG. 3) andlocked in place by means of expansion plugs 22.

The positioning of weld 15, so that it penetrates through plate 14 andinto case 13, assures a secure bond and positive seal thereat. Incontrast thereto, weld 36 of U.S. Pat. No. 3,512,612, for example, issubjected to shearing forces which may tend to separate the plate andcase. The positioning of welds l5 and 16 on a common surface of theplate further facilitates the welding operation.

Electron beam welding allows the use of a thinwalled plate and casewhich can be stamped, hydroformed or otherwise suitably formed pursuantto economical mass production techniques. The resulting relativelightness of the structurally integrated damper housing tends to reducethe parasitic mass of the damper. Otherwise stated, the total mass ofthe housing and attached crankshaft H is significantly reduced inproportion to the mass of weight 24 thereby improving damperperformance.

The use of electron beam welding, due to the inherent low heatconcentrations thereof, also prevents distortion of the housing. Thus,the various dimensional tolerances designed into the damper may be keptwithin the necessary ranges without the need for subjecting the housingto costly machining operations. In addition, the case may be filled withsilicone prior to securance of cover plate 14 thereon since the low heatconcentrations will have little, if any, effect on the silicone.

We claim:

1. A torsional vibration damper disposed for rotation about a centralaxis thereof comprising a housing having an annular weight rotatablymounted therein, said weight being encased in a plastic material, saidhousing comprising an annular case having inner and outer walls disposedparallel to said axis and connected together by a transverse side wall,extending radially outwardly from said axis, to define an annularchamber having said weight rotatably mounted therein, an annular flangeconnected to said inner wall in offset relationship with respect to saidside wall and extending radially inwardly toward said axis, a flatcircular plate abutting a free edge of said outer wall and said flangeto close said chamber, spaced annular electro-beam weld means on saidplate penetrating through said plate and into said case for securingsaid plate to each of the free edges of said outer wall and said flange,means forming an annular groove of limited depth at an outer surface ofsaid plate adjacent to each one of said weld means, each of said grooveshaving a generally V- shaped cross section and terminating at an apexthereof at a respective one of said weld means, an annular seal meanspositioned between said plate and said flange adjacent to and radiallyinwardly from the weld means securing said plate to said flange, and twodiametrically disposed port means formed through said plate tocommunicate with said chamber, each of said port means having acounterbore portion formed at an outer surface of said plate, and a leadseal and overlying expansion plug mounted in said counterbore portion.

1. A torsional vibration damper disposed for rotation about a centralaxis thereof comprising a housing having an annular weight rotatablymounted therein, said weight being encased in a plastic material, saidhousing comprising an annular case having inner and outer walls disposedparallel to said axis and connected together by a transverse side wall,extending radially outwardly from said axis, to define an annularchamber having said weight rotatably mounted therein, an annular flangeconnected to said inner wall in offset relationship with respect to saidside wall and extending radially inwardly toward said axis, a flatcircular plate abutting a free edge of said outer wall and said flangeto close said chamber, spaced annular electro-beam weld means on saidplate penetrating through said plate and into said case for securingsaid plate to each of the free edges of said outer wall and said flange,means forming an annular groove of limited depth at an outer surface ofsaid plate adjacent to each one of said weld means, each of said grooveshaving a generally V-shaped cross section and terminating at an apexthereof at a respective one of said weld means, an annular seal meanspositioned between said plate and said flange adjacent to and radiallyinwardly from the weld means securing said plate to said flange, and twodiametrically disposed port means formed through said plate tocommunicate with said chamber, each of said port means having acounterbore portion formed at an outer surface of said plate, and a leadseal and overlying expansion plug mounted in said counterbore portion.